To learn more about soils that occur in your area, this exercise will access the National Soil Survey Center Laboratory Research Database of soils throughout the United States.

1. Begin your search by entering the National Soil Characterization Database website.

2. Follow the link for "Characterization Data".

3. On the next page, place a check mark on the box for "Site Area Selection" and then use the pull down menus to set your country, state, and county, then click on "Execute Query".

4. On a separate sheet of paper, list the types of soils described for your county. If your county returns more than one soil type, select any two by placing a check mark in the box, make sure "Generate Report" is checked, then click "Continue". At the next page, choose the "Primary Characterization Report " option from the menu, and click on "Get Report".

6. When the results for each sample appear, compare the quantities of clay, silt, and sand in each sample.

a. Are they similar or do they differ dramatically?

b. What geological factors might account for the similarities and differences observed in your soil samples?

c. Do the proportions of clay, silt, and sand change in each soil horizon? What geological factors might account for this?

d. In general, is there a relationship between clay content of a soil and abundance of calcium (CA), magnesium (MG), sodium (NA), or potassium (K)?